This invention relates to an integrated coal-fired gas turbine power plant, and more particularly, to an integrated power plant and process employing a hydraulic compressor-gas turbine combined cycle.
Integrated coal-fired gas turbine power plants are well known. A typical integrated plant arrangement includes a pressurized coal combustion system wherein a gaseous effluent is produced and is employed to drive an associated expansion turbine. A mechanical compressor provides pressurized air to the coal combustion system. Such plants also typically include a secondary cycle wherein waste heat contained in the exhaust of the expansion turbine is utilized in a heat recovery steam generator to produce steam for driving a cooperating steam turbine electrical generator assembly. A plant of the foregoing type is described by Woodmansee in U.S. Pat. No. 4,150,953 assigned to the assignee hereof.
An improved plant of this type is disclosed by Applicant in copending patent application Ser. No. 069,775, filed Aug. 27, 1979 and assigned to the assignee hereof. The improved power plant described therein includes a hydraulic compressor which enables improvements in performance as well as the beneficial elimination of secondary steam cycles and of the mechanical compressor typical of conventional integrated plants. However, all integrated power plants incorporating pressurized coal combustion systems require a complicated pressurized coal feeding system. Additionally, since the gaseous effluent produced in such a plant contains contaminants detrimental to the operation of an associated gas turbine, these plants require extensive relatively high temperature gaseous effluent cleanup systems which increase both capital and power production costs.
Integrated plants which employ substantially atmospheric coal combustion systems are also known, such as that described by Willyoung in U.S. Pat. No. 116,005 which is assigned to the assignee hereof. In such a plant air is compressed by a mechanical compressor and is passed through an air heater positioned within an associated coal combustion system. In this manner, the compressed air is heated and is then passed to an expansion turbine in which it is expanded to produce useful work. The resultant expanded air is then passed to an inlet of the combustion system and is utilized therein in a coal combustion process.
Since clean heated air is expanded in an associated gas turbine rather than a gaseous effluent, an extensive gaseous effluent cleanup system is not required. Instead, a conventional relatively low temperature particulate removal system is often sufficient to clean a system exhaust, provided the exhaust has been sufficiently cooled. Similarly, no pressurized coal feeding apparatus is required. However, integrated plants of this type require bottoming cycles to efficiently utilize the heat generated in a combustion process.
More specifically, gaseous effluent is typically exhausted from an atmospheric coal combustion process at a temperature of approximately 700.degree. F. Since air exhausted from a conventional mechanical compressor is typically of a temperature of approximately 650.degree. F., there is insufficient temperature differential to allow efficient utilization this otherwise wasted heat without the employment of a bottoming cycle. However, the use of such bottoming cycles results in a significant capital cost expenditure and further complicates the operation of an integrated power plant. Moreover, these bottoming cycles typically exhibit a significant thermal lag which renders an associated integrated plant undesirable for service in quick-response applications such as in an electrical peaking power unit. Since electricity generated in such peaking plants is generally substantially more costly than that generated by base loaded plants, an integrated coal-fired gas turbine plant which would be useful in a peaking application would be highly advantageous.
In addition to the foregoing, it is also advantageous to minimize the size of a combustor in an integrated power generation system to reduce both capital costs and thermal losses. Accordingly, it is an object of the present invention to provide a new and improved integrated gas turbine power generation system and process which utilizes substantially all of the available heat energy generated therein while minimizing the size of an associated combustor.
Another object of the present invention is to provide an integrated coal-fired gas turbine power generation system which may be employed in peaking applications.
Another object of the present invention is to provide a new integrated coal-fired power generation system with improved cycle efficiency.
Still another object of the present invention is to reduce the cost and complexity of conventional integrated coal-fired gas turbine power generation systems.